1. Field of the Invention
The present invention is directed to a heart stimulator of the type having a pulse generator and an electrode system which contains at least one bipolar electrode with one pole arranged in the atrium and one pole in the ventricle, or at least two unipolar electrodes respectively arranged in the atrium and ventricle, for detecting atrial and ventricular activity.
2. Description of the Prior Art
Electrode systems of the type generally described above are disclosed in U.S. Pat. No. 4,154,247 and U.S. Pat. No. 4,567,901.
DDD pacemakers are currently used for treating patients with bradycardia. A conventional DDD pacemaker requires two electrodes, each with its own lead. One of the electrodes is placed in the atrium and the other in the ventricle. Electrical activity is sensed with the electrodes, and stimulation pulses are emitted when spontaneous electrical activity is not present.
There has long been a desire for DDD pacemakers employing only one electrode lead, i.e., a single lead DDD pacemaker. This would greatly simply implantation, compared to the currently required implantation of two separate and basically parallel leads.
The VDD pacemaker, using only one electrode with poles in the atrium and ventricle, is a step toward a single lead DDD pacemaker design. The poles in the atrium are "floating," i.e., they are normally not in direct contact with electrically active atrial tissue. The electrode system passes through both the atrium and the ventricle. This type of VDD electrode system contains three leads in instances wherein a unipolar electrode is employed in the ventricle, and contains four leads in instances wherein a bipolar electrode is employed in the ventricle.